1. Field of the Invention
The present invention relates to safety ski bindings which are adapted either to lock the toe end of a ski boot in position so as to constitute a toe abutment device or to lock the heel end of a ski boot so as to form a heel-holding device.
In more precise terms, the invention relates to the so-called multidirectional-trip ski bindings. This type of ski binding comprises a boot-retaining jaw unit mounted for pivotal displacement in the vertical direction on a body which is in turn rotatably mounted on a pivot located at right angles to the ski. A resilient mechanism is provided for maintaining the jaw unit and body in their normal positions.
Thus, in the event of torsional stress exerted on the skier's foot, the jaw unit is capable of lateral displacement by rotating with the ski-binding body about the pivot in order to permit lateral disengagement of the ski boot. However, this jaw unit is also capable of undergoing an upward pivotal displacement in order to permit disengagement of the ski boot in this direction also, either in the event of a forward fall in the case of a heel-holding device or in the event of a backward fall in the case of a toe-abutment device.
2. Description of the Prior Art
In order to achieve a satisfactory degree of safety, certain types of toe bindings or abutment devices are so designed that a forward thrust exerted on the ski boot and caused by an incipient forward fall, for example, produces a reduction in the elastic resistance acting in opposition to rotational displacement of the corresponding toe-abutment device. In point of fact, this forward thrust increases the friction forces sep up by the ski boot and consequently increases the stiffness or ski-boot release. It is therefore necessary to reduce the elastic resistance of the boot-retaining mechanism in order to ensure that the magnitude of the retaining force remains substantially the same.
Thus, French Pat. No. 2,395,046 describes a toe-abutment device in which the boot-retaining jaw unit is mounted for axial sliding motion on the rotary body of the jaw unit in such a manner as to produce a reduction in torsional elastic resistance in the event that a thrust is exerted on said jaw unit in the forward direction. The resilient mechanism provided in this abutment device consists of a piston which is housed within the rotary body and is applied by a spring against a flat face formed on the pivot. Said piston is adapted to carry two lateral extensions placed on each side of the pivot. In the event of a forward displacement of the boot-retaining jaw unit, this unit exerts a thrust on the ends of the above-mentioned lateral extensions, thereby moving the piston away from the flat face (which normally serves as a bearing surface for the piston) and thus permitting free rotational displacement of the abutment body.
In the event of a forward fall, the ski boot is therefore completely released. However such an abrupt release constitutes a potential hazard. Furthermore, the toe-abutment device described in the cited patent document does not in any way permit release of the ski boot in the event of a backward fall. A fortiori, no arrangements are therefore made to reduce elastic resistance to rotational displacement in the event of a backward fall.
French Pat. No. 2,439,601 describes a ski binding which can constitute both a heel-holding device and a toe-abutment device. This ski binding is so designed as to permit upward release of the ski boot, which is not the case with the toe-abutment device mentioned earlier. The ski binding described in this second patent comprises an end-piece which is capable of upward pivotal displacement and is carried by a body, said body being in turn rotatably mounted on a pivot which is perpendicular to the ski. This pivot has two flat faces which are oriented in opposite directions and against which are applied respectively a bearing surface formed in the end-wall of the rotary body and a piston mounted within this latter, a single spring being applied against said piston. The corresponding jaw unit is pivotally mounted directly on the rotary body of the ski binding about a transverse axis parallel to the top surface of the ski. However, this jaw unit is maintained in its normal position by a cross-pin interposed between the end-wall of the rotary body and the corresponding flat face of the pivot, the opposite ends of said cross-pin being adapted to cooperate with guide ramps provided on said jaw unit.
When this ski binding is employed as a toe-abutment device, it permits both lateral disengagement of the ski boot under the action of a very high torsional stress as well as upward disengagement of the toe end of the boot under the action of a backward fall. However, this ski binding is so designed that the jaw unit remains engaged with the corresponding end of the ski boot over a substantial range of travel.
To this end, the rotary body is capable of sliding in the rearward direction with respect to said pivot, and the boot-retaining jaw unit is in turn capable of sliding in the axial direction on said body, the axis of pivotal displacement of the jaw unit being materialized by trunnions carried by said body and engaged within slots formed in said jaw unit. Thus a rotational displacement of the body of the ski binding produces a rearward displacement of the binding and of the jaw unit.
In the event of upward displacement of the jaw unit, the procedure is the same. However, this movement is also accompanied by a movement of the bearing surface away from the rotary body with respect to the corresponding flat face of the pivot, which accordingly produces a reduction in the elastic resistance to rotational displacement of the ski-binding body.
However, when the ski binding is employed as a toe-abutment device, the above-mentioned reduction in elastic resistance to rotation takes place only in the event of a backward fall, whereas a forward fall produces no such reduction. In actual practice, however, a large number of falls experienced by skiers correspond to a complex movement of falling forward and twisting. When this occurs, it is essential to provide for a reduction in the resistance which acts in opposition to a rotational displacement. The ski binding disclosed in the cited patent fails to achieve this result.